Residual dentin thickness in mandibular premolars prepared with Gates Glidden and ParaPost drills

Statement of problem. The main factor that determines the prognosis of rest ored pulpless teeth is preservation of sound dentin. Purpose. This study evaluated the residual dentinal thickness (RDT) of mand ibular premolars after preparation of post space with Gates Glidden and Par aPost drills. Material and methods. Twelve extracted single canal mandibular premolars we re embedded in clear polyester resin to the cementoenamel junction (CEJ) in a muffle device. Three horizontal sections were made 1, 3, and 5 mm apical to the GET. Mesiodistal (MD) and faciolingual (FL) axes were carefully mar ked and the RDT was measured for each slice. Each tooth slice was reassembl ed in the muffle device with orientation pins, then secured with stabilizin g pins. This procedure was repeated after enlarging the root canal to K-40 file and preparing the coronal root canal space with Gates Glidden drills a nd ParaPost drills Nos. 3, 4, and 5. Results. Residual dentinal thickness in a MD direction was 3.77 +/- 0.51 mm in the unprepared upper slice and 2.23 +/- 0.31 mm in the No. 5 ParaPost d rill prepared lower slice, for a difference of 41%. The corresponding value s for the FL direction were 4.35 +/- 0.51 mm and 4.08 +/- 0.46 mm, respecti vely (6%). Conclusion. The average dentinal thickness 5 mm below the CEJ in the mesial and distal directions after post space preparation approached the accepted minimal 1 mm. A conservative approach to post space preparation was advoca ted.